Turbomachine with variable guide/stator blades

ABSTRACT

A turbomachine having at least one flow path, in which at least one stator blade  2  is arranged, which is variable around a rotational axis  1 , and which comprises at its radial end areas one rotary base  3  each, wherein a portion of the rotary base  3  is non-circular, when viewed in a direction of the rotational axis  1  of the stator blade  2.

This application claims priority to German Patent ApplicationDE102006052003.3 filed Nov. 3, 2006, the entirety of which isincorporated by reference herein.

The present invention relates to variable stator blades ofturbomachines, such as blowers, compressors, pumps and fans of theaxial, semi-axial or radial type. The working medium (fluid) may begaseous or liquid.

A general state of the art of such turbomachines with variable statorblades is shown in Specifications US 2004/0240990 A1 and US 2004/0115051A1, by way of example.

More particularly, this invention relates to at least one variablestator blade of a turbomachine or to a variable inlet guide vaneassembly, if applicable. The respective blading is situated within acasing, which confines the passage of fluid through at least one rotorand one stator in the outward direction. While a rotor comprises severalrotor blades attached to a rotating shaft and transfers energy to theworking medium, a stator comprises several stator blades mostly fixed inthe casing.

The aerodynamic loadability and the efficiency of turbomachines, forexample blowers, compressors, pumps and fans, is limited in particularby the growth and the separation of boundary layers in the area of theradial gaps between the blading and the casing or the hub, respectively,these gaps being necessary at the annulus rim for reasons of design. Inparticular on rotatable variable stators, the radial gaps, which may begenerated by recesses before and after the trunnion, are pronounced andentail considerable flow losses. In order to limit these losses, rotarybases of max. possible size are usually used on the inward and outwardends of the variable stators to keep small the extension of the recessesin flow direction. Now the rotary bases are usually perfectly circular.Since the diameter of the rotary bases is restricted by the distancebetween two adjacent blades, rotary bases must be provided, inparticular in the case of narrow blade spacings as increasingly appliedto modern machines, whose diameters are clearly smaller than the profilelength of the blade in the respective hub or casing area. Thus, aconsiderable radial gap before and/or behind the rotary base isinevitable. The state of the art does not provide any solution foravoiding such radial gaps on variable stators.

FIG. 1 shows, in the meridional plane, part of a state-of-the-artturbomachine in the area of one of its variable stator rows. Besides thevariable stator row proper, components in the hub area 4 and in thecasing area 5 are indicated which bear the variable stator (stator blade2) on the inner and outer side.

Not explicitly shown here, but also part of the present invention, arevariable stator arrangements which are borne in either the casing or thehub of FIG. 1, with a full radial gap being provided at the respectiveopposite blade end.

View A-A on the right-hand side of the Figure shows the inner flow pathboundary (hub) in an aspect parallel to the rotational axis of thevariable stator (stator blade 2). The state-of-the-art design here shownprovides rotary bases of the individual variable blades which areseparately borne in the hub. Here, the blade airfoil clearly protrudesbeyond the rotary base with its leading and/or trailing edge.

While the view exemplifies the rotary bases on the hub side, aprincipally equal arrangement of rotary bases is, in rotationalaxis-parallel aspect, found on the casing-side boundary of the flow pathof the turbomachine.

The present invention relates to stators (stator blade 2) which arerotatably borne at least one blade end and are variable around arotational axis 1 by a trunnion. As in all representations shown herein,inflow to the respective blade row is from the left to the right in thedirection of the bold arrow.

A broad aspect of the present invention is to provide a variable statorblade of the type specified above which, while avoiding thedisadvantages of the state of the art, is characterized by extensive oreven complete avoidance of radial partial gaps at the blade end by aspecial cutback of the otherwise circular rotary base.

The present invention provides a variable stator blade for the use in aturbomachine which features on at least one of its ends, a rotary basewhose cross-section, as viewed in the direction of the rotational axisof the variable stator (stator blade 2), significantly departs fromperfect circularity in that two straight or curved flanks are providedby cutting back the perfectly circular shape of the rotary base onopposite sides, with the rotary bases of adjacent variable stators beingborne in overlapping circular recesses in the casing or hub component,respectively.

The present invention is more fully described in the light of theaccompanying drawings, showing preferred embodiments. In the drawings,

FIG. 1 is a schematic representation of a variable stator (stator blade2) according to the state of the art,

FIG. 2 shows a solution for a variable stator in accordance with thepresent invention,

FIG. 3 shows another solution for a variable stator in accordance withthe present invention,

FIG. 4 shows yet another solution for a variable stator in accordancewith the present invention,

FIG. 5 is a schematic representation of possible rotary positions of thevariable stator in accordance with the present invention,

FIG. 6 shows a plan view of a rotary base in accordance with the presentinvention, curved flanks, view A-A,

FIG. 7 shows another plan view of a rotary base in accordance with thepresent invention, straight flanks, view A-A,

FIG. 8 gives examples for sections of rotary bases in accordance withthe present invention, section B-B.

FIG. 2 shows, in the meridional plane, part of a turbomachine in thearea of one of its variable stator rows (stator blade 2). Besides thevariable stator row proper, components in the hub area 4 and in thecasing area 5 are indicated which hold the variable stator (stator blade2) on the inner and outer side.

Not explicitly shown here, but also object of the present invention, arevariable stator arrangements which are borne in either the casing or thehub, with full radial gap at the respective opposite blade end.

View A-A on the right-hand side of the Figure shows the inner flow pathboundary (hub) in an aspect parallel to the rotational axis of thevariable stator (stator blade 2).

The inventive solution here shown provides for a special shape of therotary bases 3 disposed at the blade ends. The blade airfoil 8 here liesfully on the rotary base 3 in the area of the leading edge and protrudesbeyond the rotary base 3 with its trailing edge only. By cutting backtwo opposite rim zones of the—originally perfectly circular—rotary base3, the latter is provided with two flanks S, D which are straight in theexample here shown. Between the flank S situated in the vicinity of theconvex suction side of an airfoil and the flank D situated in thevicinity of the concave pressure side of the adjacent airfoil, a gapexists which enables the variable stator (stator blade 2) to rotatethrough a certain angular range. The present invention allows a distancebetween respective axes of rotation for adjacent blades/vanes to besmaller than a diameter of a base circle of the rotary bases 3, byproviding relieved portions on the adjacent rotary bases that provideadditional clearance between the outer edges of the adjacent rotarybases and/or which allow the adjacent rotary bases to overlap oneanother (see below).

A solution according to the present invention may also provide for anyother relative rotational position between airfoil and the cut-backrotary base 3 other than that selected in the representation in FIG. 2.

FIG. 3 shows, quite similar to FIG. 2, a variable stator row in themeridional plane. View A-A on the right-hand side of the Figure showsthe inner flow path boundary (hub) in an aspect parallel to therotational axis of the variable stator (stator blade 2). The inventivesolution here shown provides for a positioning of the airfoil on therotary base 3 which, in part of the range of variation of the stator,results in an overlap of the blade trailing edge and the rotary base 3of an adjacent stator blade 2.

Not shown here, but also in accordance with the present invention is apositioning of the airfoil, which, in part of the range of variation ofthe stator, results in an overlap of the blade leading edge and therotary base 3 of an adjacent stator blade 2.

Quite similar to FIG. 2, FIG. 4 shows a variable stator row in themeridional plane. View A-A on the right-hand side of the Figure showsthe inner flow path boundary (hub) in an aspect parallel to therotational axis 1 of the variable stator. The inventive solution hereshown provides for a complete positioning of the airfoil on the rotarybase 3. The originally perfectly circular rotary base 3 is cut back toprovide two very long flanks which in the example here shown are againstraight, but which also may be curved.

FIG. 5 shows three different rotary positions of the variable statoraccording to the present invention for:

-   a) Variation towards large stagger angles of the stator blade 2 (low    part-load range of the turbomachine)-   b) Intermediate rotary position and correspondingly maximum gap    between the flanks (intermediate part-load range of the    turbomachine)-   c) Variation towards small stagger angles of the stator blade 2    (design range and overload range of the turbomachine).

As becomes apparent from the illustration, the gap between the flanks oftwo adjacent rotary bases 3 is minimal or even equal to zero at therespective margins of the range of variation of the stator (i.e. atextremely large and small stagger angles of the variable stator blades).

For clarification of the concept according to the present invention, theabove Figures show the opposing cutbacks of the rotary base 3 as beingsymmetric to the blade rotational axis and having straight flanks.Besides this representation, the scope of solution of the presentinvention also includes flanks which are neither straight nor of equallength.

FIG. 6 shows a rotary base 3 in rotational axis-parallel view. Forclarity, the blade is omitted in the illustration. Starting out from theperfectly circular shape of the rotary base 3, two highly differentcutbacks may be provided according to the present invention whosecontours, with the rotary position of the variable stator being properlyselected, match with each other over parts of the flank. The penetrationdepths S1 and S2 into the circle of the diameter D may here differfreely from each other.

A solution according to the present invention may also provide for anycontour of the flanks S and D other than those selected in FIG. 6. Theflow-facing (wetted) surface of the rotary base 3 may, according to thepresent invention, be straight, or—to provide for a particularlyfavorable transition between rotary bases 3 of adjacent stator blades2—be inclined, beveled, wavy or otherwise contoured.

Similar to FIG. 6, FIG. 7 shows a rotary base 3 in rotationalaxis-parallel view. For clarity, the stator blade 2 is also omitted inthe illustration.

Starting out from the perfectly circular shape of the rotary base 3, twostraight flanks with different penetration depths S1 and S2 wereselected. In this representation, as well as in the previous ones,solutions according to the present invention are shown in which theedges produced at the flanks are rectangular to the surface of therotary base. Departing from this concept, it can be particularlyfavorable according to the present invention to provide the surface ofthe flank inclined, i.e. not parallel, in relation to the bladerotational axis 1 and/or with a special contour.

For clarity, FIG. 8 shows the section B-B through the rotary base 3defined in FIG. 7 and a small part of the airfoil 8. While the upperpart of the illustration shows the solution according to the presentinvention with rectangular edges of the flanks (rotary base withoutinclination of the flanks S and D (orientation approx. parallel to therotational axis)), the lower part of the illustration exemplifies twomatching inclinations/contours of the flanks S and D (rotary base withinclination and contouring of the flanks S and D). Here as well, theflow-facing (wetted) surface of the rotary base 3 may, according to thepresent invention, be straight or—to provide for a particularlyfavorable transition between rotary bases 3 of adjacent stator blades2—be inclined, beveled, wavy or otherwise contoured.

LIST OF REFERENCE NUMERALS

-   1 Rotational axis-   2 Stator blade (variable stator)-   3 Rotary base-   4 Hub component-   5 Casing component-   6 Piercing point of blade rotational axis 1-   7 Flow-facing (wetted) surface-   8 Blade airfoil

1. A turbomachine comprising: at least one flow duct, at least one of aguide blade and a stator blade arranged in the flow duct which isrotatable around a rotational axis, and which comprises at its radialend areas one rotary base each, wherein the rotary base includes asection that is non-circular, when viewed in a direction of therotational axis.
 2. The turbomachine of claim 1, wherein thenon-circular section of the rotary base includes two flanks of at leastone of a straight and a curved configuration, the flanks being relievedportions on opposite sides of a base circle of the rotary base.
 3. Theturbomachine of claim 2, wherein a least one of a casing component and ahub component of the turbomachine includes overlapping circular recessesin which rotary bases of adjacent blades are positioned.
 4. Theturbomachine of claim 3, wherein the two flanks are straight andparallel to one another.
 5. The turbomachine of claim 3, wherein the twoflanks have curved portions.
 6. The turbomachine of claim 4, whereineach of the flanks is the same length.
 7. The turbomachine of claim 4,wherein each of the flanks is the same distance from the rotationalaxis.
 8. The turbomachine of claim 4, wherein each of the flanks is adifferent distance from the rotational axis.
 9. The turbomachine ofclaim 1, wherein each of the flanks is parallel to the rotational axis.10. The turbomachine of claim 1, wherein each of the flanks includes atleast one of an inclined portion and a contoured portion in relation tothe rotational axis.
 11. The turbomachine of claim 1, wherein a leastone of a casing component and a hub component of the turbomachineincludes overlapping circular recesses in which rotary bases of adjacentblades are positioned.
 12. The turbomachine of claim 2, wherein the twoflanks are straight and parallel to one another.
 13. The turbomachine ofclaim 2, wherein the two flanks have curved portions.
 14. Theturbomachine of claim 2, wherein each of the flanks is the same length.15. The turbomachine of claim 2, wherein each of the flanks is adifferent distance from the rotational axis.
 16. The turbomachine ofclaim 1, wherein each of the flanks includes at least one of an inclinedportion and a contoured portion in relation to the rotational axis sothat adjacent rotary bases can overlap one another.
 17. A turbomachinecomprising: at least one flow duct, at least one row of guide/statorblades positioned in the flow duct, each of which is rotatable around arotational axis and which comprises at its radial end areas one rotarybase each, wherein the rotary bases from at least one blade in adjacentblade pairs include portions recessed from a base rotary circle toprovide clearance between the adjacent rotary bases such that a distancebetween the respective rotational axes of the adjacent blade pair issmaller than a diameter of a base circle of the rotary bases.
 18. Theturbomachine of claim 17, wherein the recessed portions provideclearance between outer edges of the adjacent rotary bases.
 19. Theturbomachine of claim 17, wherein the recessed portions allow outeredges of the adjacent rotary bases to overlap one another.
 20. Theturbomachine of claim 17, wherein the rotary bases from both blades inadjacent blade pairs have recessed portions.